Microwave device



Sept. 8, 1942. woLFF MICROWAVE DEVICE Filed July 21, 1939 za'as'sis Irving Wolf,

Radio Delaware MICROWAVE DEVICE Herchantville, N. J'., assignor to tion of America, a corporation ot Application July 21, 1939, serial No. 235,730 17 claims. (ci. aso-a7) -'li'liis invention relates to microwave devices and more especially to a centimeter wave thermionic tube oi the velocity modulation type.

Thermionic tubes, designed for ultra high irequency oscillations, have been arranged so that the electrons o! a stream o r beam of electrons are grouped in fast and slow moving electronic clouds. Such grouping as a function of velocity isbrought about by the suitable application of electric iields and is known as velocity modulation.

The present invention has for one of its objects the provision oi improved means for velocity f modulating a stream of electrons. Another object is to provide an emcient velocity modulation tube. Another object is to provide a microwave tube of the velocity modulation type occupying a smaller volume than heretofore considered practical. An additional object is to provide means Y for applying multiple velocity modulation to a stream of electrons.

The invention will be described by reference to the accompanying drawing which represents in a perspective view'one embodiment of the invention.- A source o! electrons I, truncated conical controlling electrodes 3, 3 and a .cylindrical electrode 'I-are arranged within-one end of an evacuated envelope 9 which preferably includes a conductive nlm I0. A ilrst half wave split anode electrode Il is mounted within the envelope adjacent the cylindricalelectrode and in axial alignment therewith. A second half wave split anode electrode I3 is mounted within the envelope coaxially with and spaced from the iirst mentioned half wave electrode. Transmission lines l5, i1 are connected respectively to the rst and second half wave electrodes and are terminated respectively in an input circuit I9 and an output circuit 2|', represented by way of example as antennas. The ends of each oi the two half wave split anode electrodes are connected respectively by short circuiting rings 23. c

A hollow conical collecting electrode 25 is disposed between the adjacent ends of the half wave electrodes l l, i3. A second collecting electrode 21, composed of a plurality of triangular shape radially mounted vanes 29, is mounted adjacent the end of the second half wave split anode electrode. The cylindrical electrode 1, and split anode electrodes Il, I3 are biased positively with respect to the electron source I. The controlling electrodes 3, 5 and the collecting electrodes 25, 21 are also biased positively.

The envelope is surrounded by a solenoid 3U,

lines, and, being emitted from a plurality oi points, would ynot kbe beamed narrowly but would be spread over a considerable area. Under the iniluence ofthe magnetic and electric fields, the electrons spiral outwardly, and at the same time the increased magnetic eld and the distribution of the electric eld near the electron source, followed by the decreased magnetic iield and increased electric field, cause the electrons to form, iirst, a hollow rotating and advancing cylinder of increasing diameter, and,` second, a rotating hollow cylinder. The cylinder advances continuously from the gun toward the final collecting electrode 2.

rotation period oi' the electrons within the split anode electrode il and i3 is the same as the period oi the currents applied to the input transmission line it, electrons will pass the slit between the anode electrodes in the same phase. Ii' desired, more slits can be used, in which case the, period of the applied current would be a higher multiple of the rotation period. Therefore. certain electrons will be decelerated while others will be accelerated. The accelerated electrons will have the radius of their paths increased; the decelerated electrons vwill have the radius of their paths decreased. The decelerated which is shown in section to avoid complicating 55 electrons, moving in smaller circles, will be collected by the conical electrode 25, which is preierably designed to dissipate the heat developed by the electron impact.

After the removal oi the slower electrons, a

rotatingcylinder oi' electrons of variable charge density remains. This generates an amplified voltage on the second split anode electrodev I3. The amplified voltage is transferred by the transmission line il to the output circuit 2|. The electrons passing through the second or output split anode electrode strike the flanges of the iinal collecting electrode 21. 'Ihe anges, duly polarized and being radially arranged andY being oi triangular shape, inuence the electron paths so that the electrons getting within the influence oi one iiange will be likely to hit the next one.

It the magnetic neld is so adjusted that the Any secondary electrons emitted by the impact will be trapped within the ilanges. The final collecting electrode Iis made preferably of a material which will radiate the heat generated by electron impact without liberating gases.

Thus the invention has been described as a microwave amplier of the velocity modulation type. The electrons rotate within split anode electrodes to form therein hollow cylinders of electrons. The electrons advance toward collecting electrodes. In the first split anode electrode the electrons are grouped or modulated to form a variable charge density and the slower electrons are collected. The thus modulated electrons generate amplified voltages in the second split anode electrode. The electrons are collected by a final electrode. The number of modulations within the split anode electrode depends upon the rate at which the electrons advance toward the ilnal electrode. A multiple number of modulations may be readily and eiliciently obtained within a vsmall space.

The number of rotations the electrons make insidethe split electrode mustbe adjusted, having several factors in mind: The greater the number of rotations, the greater the sensitivity. However, the width of the pass band ofthe system becomes less. Also, a tendency towards regeneration becomes greater since the electrons with reduced orbit diameters have less eil'ect on the electrodes and, .to a certain extent, charge density effects are obtained even before the slower moving electrons are removed. If the input I9 and the output 2l are coupled, feedback, in appropriate phase, will cause-continuous oscillations to be generated.

I claim as my inventiont 1. A microwave device including in combination a source of electrons, controlling electrodes, a first and a second split anode electrode, means for forming electrons emitted from said source into an advancing rotating substantially hollow cylinder of electrons, means for directing said cylinder of electrons through said split anode electrodes, means for applying alternating currents to one of said split anode electrodes, means for adjusting the rotational rate of said electrons Within one of said split anode electrodes to correspond to the period of said alternating currents so that certain electrons are accelerated and others decelerated and thereby arranged in rotating variable charge density groups, means for directing the accelerated electrons of said variable charge-density electrons groups through the other of said split yanode electrodes so that voltages are generated therein, vand means for utilizing said voltages.

2. In a device `of the character of claim l, means for collecting said decelerated electrons.

3. In a device of the character of claim 1, means for collecting the electrons passing hrughsaid last mentioned 'split anode elecro e.

4. In a device of the character of .claim 1, means for collecting said decelerated electrons, and means for collecting the electrons passing through said last mentioned split anode electrode.

5. A microwave device including in combination a source of electrons, electron' controlling electrodes', a pair of half wave split anode electrodes coaxially arranged with respect to said source and in spaced relation, means for forming electrons emitted from said gun into an advancing rotating substantially hollow cylinder of electrons, means for directing said cylinder of electrons through said split anode electrodes, an input circuit, means for impressing alternating currents applied to said input circuit upon the nrst of said split anode electrodes, means for adjusting the rotational period ot said cylinder oi electrons to correspond to the period of said alternating currents so that certain of the electrons of said cylinder are accelerated and others decelerated, means for collecting the decelerated electrons whereby' the remaining electrons form variable charge density groups in the rotating cylinder, means `for passing the variable charge density electron groups through said second split anode-electrode to generate voltages therein. an output circuit for utilizing said voltages, and a collecting electrode for collecting electrons passing through said second split anode electrode.

6. In a device of the .character described, an evacuated envelope including a source oi electrons, means for establishing a magnetic iield, means for establishing an electric ileld, means for adjusting at least one of said ilelds so that the electrons from said source form a substantially hollow rotating electronic cylinder of increasing diameter, and means for converting said cylinder of increasing diameter into a cylinder of substantially constant diameter.

"1. In a device of the character described, an evacuated envelope including a source of electrons, means for establishing a non-uniform magnetic ileld, means for establishing an'lelectric neld, means for adjusting at least one oi said fields so that the electrons from said source form a substantially hollow rotating and advancing electronic cylinder oi increasing diameter, and means for converting said cylinder of increasing diameter into a cylinder of substantially constant diameter.

8. In a device of the character described, an

evacuated envelope including a source of electrons, means for establishing' an electric ileld, means for establishing a magnetic field o! increasing strength adjacent said source, means for adjusting at least one of said fields so that the electrons from said source form a substantially hollow rotating electronic cylinder of increasing diameter, and means for converting said cylinder of increasing diameter into a cylinder of substantially constant diameter.

9. In a device of the character described, an evacuated envelope including a source of electrons, means for establishing a magnetic ileld, hollow truncated conical electrodes for establishing electric nelds, said magnetic and electric nelds being arranged to form the electrons emitted from said source into a rotating substantially hollow cylinder oi 'increasing diameter, and means for converting said cylinder of increasing diameter into a cylinder of substantially constant diameter.

10. In a.v device of the character described, means for establishing a substantially hollow rotating and advancing electronic cylinder, and a collecting electrode for said electrons, said electrode including a plurality of vanes arranged along the line oisaid advancing electrons and increasing in width along said line. i 11. In a device oi the character described.

means for establishing a substantially' hollow.

rotating and advancing electronic cylinder. and a collecting electrode for said electrons, said electrode including a plurality of vanes' arranged in` intersecting planes and having increasing area along the line of said advancing electrons whereby secondary electrons emitted by the collection van'es.

proximity to the electron stream, the said 'gap being of suincient length so that individual electrons are caused to pass the gap a plurality of times, means for impressing a high frequency voltage between the said conducting members, thereby to produce variations in the 'orbital velocity of the various electrons as a result of the potential gradients developed across the said gap, and energy-abstracting means positioned to be affected by variations existing in the electron stream at a point which is axially displaced from the said gap.

13. High frequency apparatus including means for producing a stream of orbitally moving electrons in which the center of orbital motion progresses along a given axis, a pair of semi-cylindrical conductive parts which are juxtaposed to dene a cylindrical chamber arranged for traversal by the electron stream, the said parts being mutually spaced to provide axially extending gaps between their juxtaposededges, means for impressing a high frequency voltage between the semi-cylindrical parts so as to vary the orbital velocity of the various electrons in accordance with the potential gradients thus developed across the said gaps, a second pair of semi-cylindrical conducting parts axially displaced from the nrst pair and arranged to dene a second hollow chamber which is traversed by the electron stream after its traversal of the nrst chamber, said second pair of parts beingalso mutually spaced to provide axially extending gaps between their juxtaposed edges, said gaps being generally parallel to the mst-mentioned gaps, and circuit means connected between the second pair of parts so as to be excited thereby inac- .cordance with variations existing in the electron stream vupon its traversal of the said second chamber.

i4. High frequency apparatus including.' a source of electrons, means dening a chamber traversed by electrons emittedrom said source, spaced conductive members adjacent the path of the electrons and providing between them a narrow gap which extends longitudinally of the chamber, means connecting with the said con-V ductive members for impressing between them a cyclically varying voltage of predetermined irequency,.means including a source of magnetic ux for causing the electrons traversing the chamber to follow a generally helical path of suoli character that the individual electrons are brought several times into proximity with said gap before passing beyond its extremity, the average orbital transit time of the electrons being appropriete to assure that the electron velocity variations produced at the said gap are cumulative for each successive electron passage. and energyabstracting means adaptent@ be affected by the variations existing in the .stream at a region which is displaced from the said flrst-namedr yregion in a direction along the axis oi. the electron path. f

15. High frequency apparatus including means for producing a stream of orbitally moving electrons in which the center of orbital motion progresses along a given axis, a pairof spaced conducting members dening an elongated gap f which extends generally parallel to said axis in proximity to the electron stream, the said gap being vof suilicient length sothat individual electrons are caused to pass the gap a plurality of timesf means for'impressing a high frequency voltage between the said conducting members thereby to produce variations in the orbital velocity of the various electrons as a result of the potential gradients developed across the said gap, additional spaced conducting members denning a second elongated gap extending generally parallel to the rst gap in a region which is axially displaced therefrom, and' circuit means connected with the said additional conducting members and adapted to be excited thereby in accordance with variations existing in the electron stream upon its traversal of thesaid second gap.

16. High frequency apparatus including means for producing a stream of orbitally moving electrons in which the center of orbital motion progresses along a given axis, spaced conducting members denning a pair of circumferentially displaced parallely gaps which extend substantially parallel to the axis of the electron stream in close proximity to the stream, each gap being of. sufmon. means for producing cyclicallp varying potential gradients across the said gaps so as to cause recurrent variations in the orbital velocity of the electrons which traverse the gaps, the spacing of the gaps being so correlated to the average velocity of the electrons as to assure the occurrence oi' cumulative effects at the twg gaps, and energy-abstracting means positioned to be aiected by variations existing inthe electron stream at a region which is axially displaced from dit the saidy sans.

i7. High frequency apparatus including means for producing a stream of orbitally moving electrons in which the center of orbital motion prograsses along a given axis, a pair of semi-cylindrical conductive parts which are juxtaposed to denne a cylindrical chamber varranged icr traversal by the electrons stream, the said parts being mutually spaced to provide axially extending gaps between their juxtaposed edges, means for impressinga high frequency voltage between the semi-cylindrical parts so Aas to vary the orbital velocity of the various electrons in accordance with the potential gradients thus developed across the said gaps, and energy-abstracting means arranged to be affected by the variations existing in the electron stream subsequent to its traversal of the said chamber.

- IRVING WGLFF. 

